Aluminum alloy for heated bed?

Hi all, quick question, I'm about to have some parts water-cut and need to buy the aluminum sheets.
I wanted to buy MIC6 but it seems that it doesn't exists around here, so what would be a good alloy for the heated bed?

Where are you located? Alca5 is a Canadian (quasi)equivalent of Mic 6.

As well as being flat, the desired properties of the cast plates are that they are indeed cast, and have a relaxed grain structure. Wrought metal, such as 6xxx series, 7xxx series, have been cold worked (or hot worked) and have stresses inside which can cause more movement when cut or heated.

As deckingman says, "aluminum tooling plate" is the generic term – but to be more specific, you want CAST aluminum tooling plate.

I am using a 5mm thick standard alu sheet that is used for constructional purposes. I have no clue as to what alloy it. I am sure it is less flat as machined tooling plate. I think however that regardless of the alloy the heat transfer characteristics will always be better that using a borosillicate glass, I used my sheet as a base to glue PEI to, and I am pretty confident that there is more thickness variation in the PEI than in the alu, so my guess was that there is really no need for expensive tooling plate. I had two sheets waterjetted 30cm in diameter for 15 Euro's each and it is performing great. I am confident that 5mm is stiff enough to resist the inevitable bending of the Onyx bed at 20V. My duet mesh compensation routine tells me that I have about 0.06 uneveness, and that may be higher than some other folks, but it already is much better than when I was using bare glass,

Thanks DeltaCon, that good to hear considering that my options are quite limited around here.

I've just came back and boy… I love my country. When I asked the seller about MiC6, Alca5 or just about cast aluminum, he gave "that look". You kwow, the one you get when they think you are speaking in another language.
Good to know that this is a place that only sells aluminum, so you might think they know their stuff.

Anyway, cast aluminum is out of reach for me, so I've bought 7075 for all structural parts and it will be also used for the heated bed.
On top of it will be a 4mm glass and then the PEI. Let's hope it stays flat.

If not, then I must consider getting MiC6 from the states or somewhere else.

Haha, that was the same here in the Netherlands… People doing constructional work with aluminium usually are hard working noobs. If you want advise on your material you should go to a manufacturer. But they are usually not interested in selling a 30cm sheet There are probably constructional companies that build things like packing machines, CNC machines or say 3D printers that do now their stuff, but hey, it will cost more than 15 bucks a sheet

Just an off-topic question: why putting glass on your alu bed instead of just buying a thicker alu bed? In my opinion it is a lot easier to just glue the pei directly to the alu.

…...............................Just an off-topic question: why putting glass on your alu bed instead of just buying a thicker alu bed? In my opinion it is a lot easier to just glue the pei directly to the alu.

Many of us find that having a removable print surface is very advantageous. It means that as soon as one print is finished, you can slide out one piece of glass, slide another in and start printing again straight away without having to wait for the bed to cool and heat up again. You can also use different surfaces on each piece of glass. e.g PEI on one, Blue tape on another, or nothing at all on a third. If you damage PEI and have to remove it, you'll likely damage the expensive aluminium plate too. Float glass is a lot cheaper to replace.

Yes, that's a good way of using the glass. Float glass is also cheap around here. PEI is great for ABS and PLA but I'm currently printing a lot with PETg and it sticks too damn well to it. Might consider using something else there.

…...............................Just an off-topic question: why putting glass on your alu bed instead of just buying a thicker alu bed? In my opinion it is a lot easier to just glue the pei directly to the alu.

Many of us find that having a removable print surface is very advantageous. It means that as soon as one print is finished, you can slide out one piece of glass, slide another in and start printing again straight away without having to wait for the bed to cool and heat up again. You can also use different surfaces on each piece of glass. e.g PEI on one, Blue tape on another, or nothing at all on a third. If you damage PEI and have to remove it, you'll likely damage the expensive aluminium plate too. Float glass is a lot cheaper to replace.

Also I find that when I print large PLA parts on PEI they often stick too well to release easily. Putting the bed+print in the freezer for a little while releases the print.

Yes, but changing beds is also possible with alu beds, as it is with glass. At least if you have a PCB style heater like Onyx
I would not recommend normal floatglass because it is just not heat resistant enough. It breaks and splinters easily under thermal stress. Borosillicate is better of course, but more expensive then thick alu sheets

Float glass is entirely adequate provided that you have an aluminium heat spreader between it and the heater so that it gets heated evenly. I have been printing on float glass on top of aluminium for nearly 4 years. The only issue I have had with it is that a couple of times prints have stuck to the glass so well that when the print was eventually released, it brought a small chip of glass with it - but other people report that happening with borosilicate glass beds too.

Just a word on aluminum heated build plates.
I have a 300mm x 600mm build machine. I originally began using 12 mm cast aluminum with a silicon heater glued to the underside of the build platform.. I ran into nothing but problems with this ….as it headed I could actually measure the warping of the plate every time the heater would cycle regardless if it was in bang bang mode or pid mode. This was driving me crazy. The solution was to go with granite in my case I used 19mm thick polished one side and then gluing the heater pad to the underside. What a difference....I can now print the whole platform without any issues. My first layer adhesion was great...(I use a PLA Glue Water Slurry to paint on the granite) ....think twice before using aluminum

Float glass is entirely adequate provided that you have an aluminium heat spreader between it and the heater so that it gets heated evenly. I have been printing on float glass on top of aluminium for nearly 4 years. The only issue I have had with it is that a couple of times prints have stuck to the glass so well that when the print was eventually released, it brought a small chip of glass with it - but other people report that happening with borosilicate glass beds too.

David, at what kind of max bed temps have you been printing ordinary floatglas if I may ask? And how thick a glass was it?
It is not only uneven heat that causes a problem, it is also heating too quick to too high temps. I can imagine going to 90C on a 12V heater (which takes many minutes) is no problem. But when on 24V or AC mains you could heat to 120C in a minute. I don't think a 4mm ordinary floatsheet will endure that very long. And if it brakes you can get very small sharp splinters. I know you know your stuff, but I think th3d-print scene uses boro glass for a valid reason.

Just a word on aluminum heated build plates.
I have a 300mm x 600mm build machine. I originally began using 12 mm cast aluminum with a silicon heater glued to the underside of the build platform.. I ran into nothing but problems with this ….as it headed I could actually measure the warping of the plate every time the heater would cycle regardless if it was in bang bang mode or pid mode. This was driving me crazy. The solution was to go with granite in my case I used 19mm thick polished one side and then gluing the heater pad to the underside. What a difference....I can now print the whole platform without any issues. My first layer adhesion was great...(I use a PLA Glue Water Slurry to paint on the granite) ....think twice before using aluminum

Too what deviation did the heating of a 12mm alu plate lead? And to what temperatures were you heating? I do see significant other probe values at room temp and at 90C, for sure, but I don't think it is the alu bending. I can see that my Onyx is waving creating space between the alu and the the Onyx. I use three clams to fit the plate, so I get a fairly even surface. Nothing Duet autocalibration can't handle

…..................I would not recommend normal floatglass because it is just not heat resistant enough. It breaks and splinters easily under thermal stress. Borosillicate is better of course, but more expensive then thick alu sheets

As another long term user of float glass, I have to disagree. It's sudden thermal shock that might cause it to fracture, but that situation does not apply when using it over a thick aluminium base. Borosilicate glass is prone to being easily chipped, for example when trying to remove a large printed part which has adhered a little too well. I have 3 sheets of 400m x 400 x 6mm float glass that I regularly swap between. From time to time I have accidentally dropped one or dropped something heavy on top of one and never had an issue- it's surprising;y difficult to break. A word of warning though - do not be tempted to have the glass toughened as the toughening process will cause it to distort (I know from experience) - plain float glass is best IMO.

Edit. I've used it at 120 deg C with PrintBite stuck to it in attempt to get that to work, and I have a 400W 240v mains heater. I've also read many many posts from people who have never tried float glass telling me that it can't be used.

…..................I would not recommend normal floatglass because it is just not heat resistant enough. It breaks and splinters easily under thermal stress. Borosillicate is better of course, but more expensive then thick alu sheets

As another long term user of float glass, I have to disagree. It's sudden thermal shock that might cause it to fracture, but that situation does not apply when using it over a thick aluminium base. Borosilicate glass is prone to being easily chipped, for example when trying to remove a large printed part which has adhered a little too well. I have 3 sheets of 400m x 400 x 6mm float glass that I regularly swap between. From time to time I have accidentally dropped one or dropped something heavy on top of one and never had an issue- it's surprising;y difficult to break. A word of warning though - do not be tempted to have the glass toughened as the toughening process will cause it to distort (I know from experience) - plain float glass is best IMO.

Edit. I've used it at 120 deg C with PrintBite stuck to it in attempt to get that to work, and I have a 400W 240v mains heater. I've also read many many posts from people who have never tried float glass telling me that it can't be used.

(as a motivation to actually read it: glass shards were stuck into the wall…)

That just demonstrates why it's not a good idea to stick a heater, which will have local hot spots, directly onto the back of a sheet of glass. We are talking about using glass on top of a thick aluminium heat spreader.

Float glass is entirely adequate provided that you have an aluminium heat spreader between it and the heater so that it gets heated evenly. I have been printing on float glass on top of aluminium for nearly 4 years. The only issue I have had with it is that a couple of times prints have stuck to the glass so well that when the print was eventually released, it brought a small chip of glass with it - but other people report that happening with borosilicate glass beds too.

David, at what kind of max bed temps have you been printing ordinary floatglas if I may ask? And how thick a glass was it?
It is not only uneven heat that causes a problem, it is also heating too quick to too high temps. I can imagine going to 90C on a 12V heater (which takes many minutes) is no problem. But when on 24V or AC mains you could heat to 120C in a minute. I don't think a 4mm ordinary floatsheet will endure that very long. And if it brakes you can get very small sharp splinters. I know you know your stuff, but I think th3d-print scene uses boro glass for a valid reason.

Mostly I print with a bed temperature of 70C, but I had a phase of printing ABS using 110C. The bed is 5mm thick 330mm diameter aluminium with a 350W AC mains heater on the underside, and I had 4mm thick 330mm diameter float glass on top of it.

I also know of someone using a 3mm 210x210mm sheet directly on top of a PCB heater at 100C bed temperature, but I don't advise that.